var a;
a = 10;
a = 'hello';
//指定一个类型就好了
var b;
var c;
var d = true;
// TS2322: Type '"hello"' is not assignable to type 'number'.
// b = 'hello';//不允许
b = 10; //允许
c = 'love';
//主动类型推断
var e = false;
e = true;
function sum(a, b) {
    return a + b;
}
console.log(sum(100, '100'));
